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pythonlistlist-comprehension

How can I do assignment in a List Comprehension?

Generally, whenever I do a for loop in python, I try to convert it into a list comprehension. Here, I have a for loop where a variable value is altered after each loop.

k=5
for x in range(1,6):
    k*=x
    print(k)
#output
5
10
30
120
600

I want to perform this operation in list comprehension. I tried doing but I was getting syntax error. I tried this below:

[k*=x for x in range(1,6)]
Solution

  • You can use walrus operator (python 3.8+):

    k = 5
output = [k := k * x for x in range(1, 6)]

print(output) # [5, 10, 30, 120, 600]

    But this pattern is not welcomed by some people.

    Another option would be to use itertools.accumulate:

    from itertools import accumulate
from operator import mul

output = accumulate(range(1, 6), mul, initial=5)

print(*output) # 5 5 10 30 120 600

    In this case the initial value 5 is attached at the beginning.